Free-Init: Scan-Free, Motion-Free, and Correspondence-Free Initialization for Doppler LiDAR-Inertial Systems

2026-09-24

AI Summary

This study addresses the limitations of online initialization for LiDAR-inertial systems, which typically depend on motion compensation, sufficient excitation, and map matching. To overcome these constraints, this work proposes Free-Init, a novel framework that pioneers the exploitation of the Doppler effect in FMCW LiDAR. By employing non-inertial kinematic modeling and pointwise velocity-IMU tightly coupled fusion, the method achieves robust initialization without requiring deskewing, specific motion patterns, or point correspondences, thereby supporting arbitrary initial states ranging from stationary to highly dynamic conditions. The system operates at output frequencies exceeding 10 kHz and features plug-and-play capability. Extensive evaluations across multiple platforms and complex scenarios validate its rapid convergence and high robustness.

Abstract

Robust initialization is crucial for online systems. In the letter, a high-frequency and resilient initialization framework is designed for LiDAR-inertial systems, leveraging both inertial sensors and Doppler LiDAR. The innovative FMCW Doppler LiDAR opens up a novel avenue for robotic sensing by capturing not only point range but also Doppler velocity via the intrinsic Doppler effect. By fusing point-wise Doppler velocity with inertial measurements under non-inertial kinematics, the proposed framework, Free-Init, eliminates reliance on motion undistortion of LiDAR scans, excitation motions, and map correspondences during the initialization phase. Free-Init is also plug-and-play compatible with typical LiDAR-inertial systems and is versatile to handle a wide range of initial motions when the system starts, including stationary, dynamic, and even violent motions. The embedded Doppler-inertial velocimeter ensures fast convergence and high-frequency performance, delivering outputs exceeding 10 kHz. Comprehensive experiments on diverse platforms and across myriad motion scenes validate the framework's effectiveness. The results demonstrate the superior performance of Free-Init, highlighting the necessity of fast, resilient, and dynamic initialization for online systems.

Problem

• Initialization
• Doppler LiDAR
• Inertial Systems
• Robustness
• Online Systems

Innovation

• Doppler LiDAR
• Initialization
• Inertial fusion
• FMCW
• Plug-and-play